The present invention relates generally to devices for delivering gases having a controlled vapor level and temperature to a delivery point, and more particularly to humidifier devices employing disposable humidifier cartridges which receive water from an adjacent container.
When a normally healthy person breathes atmospheric air, his air passages supply heat and moisture to the inhaled gases, with the body being able to supply the required amount of heat and moisture. However, when subject to certain medical conditions, a patient's mechanism of supplying heat and moisture is disrupted, and it becomes necessary to provide an artificial system for warming inspired gases to a point at or near normal body temperature before the gas is delivered to the patient. Accordingly, it is necessary to humidify the inspired gases to a level at or near full (100%) moisture saturation.
Conventional systems for providing heated and moisturized respiratory gases basically fall into two groups: nebulizers, which produce aerosols of fine water droplets, and heated humidifiers, which supply heat and moisture to a gas by the passage of the gas through or over a heated water bath or evaporative surface. The present invention is concerned with the latter group of devices.
One such humidifier system includes a rigid, refillable water container designed to be placed upon a base unit having a heating element. The container is divided into an upper reservoir section, and a lower humidifier chamber by a partition having a small diameter vertical port therein. Water flows by gravity from the reservoir section through the port into the humidifier chamber, through which a stream of gas flows to be heated and humidified.
A float valve controls the water level in the humidifier by sealing the port when the maximum specified water level is attained. As water is used, the water level in the humidifier chamber falls, opening the port to allow additional water to enter from the reservoir section. A major disadvantage of this type of humidifier is that the reservoir must be refilled from another container, a process which requires that the reservoir be opened, subjecting it to bacterial contamination. Another disadvantage of the rigid, capped reservoir section is that the reservoir is not vented, which may interfere with the free flow of water due to the creation of a vacuum in the reservoir.
Another conventional system employs a vertically oriented, cylindrical humidifier chamber which is fed water through a port in the lower end. A tube connects the lower end of the humidifier chamber to the lower end of a rigid, disposable water container. An upper portion of the humidifier chamber includes gas inlet and delivery ports, as well as a vent port connecting the chamber with an upper end of the water supply container. A float valve in the humidifier chamber blocks the flow of air into the vent line as the water level rises in the chamber, thus preventing the entry of water into the humidifier chamber from the supply container.
By venting the supply container, the problem of irregular water flow identified in the previous example is eliminated. However, a potentially more serious problem is created, i.e., the possibility of airborne bacteria exhaled by the patient entering the humidifier chamber and contaminating the supply water through the vent tube.
There are several types of heated humidifier units presently available to hospitals, and many of these have the inherent problems of susceptibility to contamination, and relatively excessive operator maintenance. Of these available units, many are designed for use with relatively expensive heater base units which are an obstacle to conversion to more efficient and less contamination-prone disposable devices.
Thus, there is a need for a disposable humidifier system which does not mix the patient's exhalate with the supply water, which prevents bacterial contamination of the supply water by other means, and which is adaptable to at least one and preferably more of the variety of evaporative heater base units currently in use by hospitals and respiratory practitioners. There is also a need for a cartridge humidifier system which is simple in its operation, and is inexpensive to manufacture and assemble.